Embodiments of the present invention relate to a method and a device for detecting a bright dot or a dark dot in liquid crystal display.
Liquid crystal displays (TFT-LCDs) possess advantages of small volume, low power consumption, low radiation, etc., and are gradually prevailing in the market of flat plate displays. Generally, a liquid crystal display comprises an array substrate and a color filter substrate attached together and sandwiching a liquid crystal layer therebetween. Gate lines for providing scanning signals, data lines for providing data signals, pixel electrodes, and array substrate electrodes for providing common voltage are provided on the array substrate, and a black matrix, color filters and a color filter substrate common electrode are provided on the color filter substrate.
Generally, detection is required after the array substrate and the color filter substrate are attached together to form a liquid crystal cell in order to rule out defective products and then repair the defect. FIG. 6 is a schematic view showing the structure of a conventional device for detecting a bright dot or a dark dot in a LCD. The method utilizes the common electrodes for detecting a bright dot or a dark dot. As shown in FIG. 6, the conventional detection device mainly comprises a voltage input terminal 20, an operational amplifier A, a first resistance R1, a second resistance R2 and a voltage output terminal 40. The voltage input terminal 20 is connected with a power source (not shown), and the voltage output terminal 40 is connected with the array substrate common electrode and the color filter substrate common electrode. By applying a same detection voltage to the array substrate common electrode and the color filter substrate common electrode, a bright dot or a dark dot in the LCD can be observed.
In addition, a bright dot or a dark dot in a LCD may result from an array substrate defect or a defect occurring in the liquid crystal cell. Although the bright dot or the dark dot in a LCD can be observed through the conventional detection device, it is impossible by using the conventional detection device to distinguish that the bright dot or the dark dot is resulted from an array substrate defect or from a liquid crystal cell defect. In practice, it is important for subsequent repair processing to determine the type of the defect. After cell process to assemble the substrates together, the array substrate defect can be repaired by a laser repair process, but feasible method for repairing the liquid crystal cell defect have not been developed yet. In addition, the type of the defects can typically be determined with microscopy; however, it is impossible to detect some bright dots or dark dots defects (for example, a defect occurring in the TFT channel region, the region shielded by the black matrix and the like) with microscopy only. Usually, the product in which the type of the defect cannot be determined may be discarded, and thus the production cost is increased and the production efficiency is decreased.